The calibration of 35S or 32P with 14C-labeled brain paste or 14C-plastic standards for quantitative autoradiography using LKB Ultrofilm or Amersham Hyperfilm.

The relationship between 14C-labeled brain paste or plastic standards and 35S- or 32P-labeled brain paste was characterized with quantitative autoradiography. Film was exposed to both sets of 14C-labeled standards and 35S- and 32P-labeled standards for 15-148 h and the film was analyzed with computer densitometry. Subsequently, the tissue pastes were scraped from the slides, dissolved in tissue solubilizer and radioactivity determined by scintillation spectroscopy. A linear relationship was observed between the plastic and brain paste 14C standards as well as between both sets of 14C-labeled standards and 35S-labeled brain paste standards. The 32P-labeled standards demonstrated a poor linear relationship with the 14C-labeled standards and greater variability in the autoradiographic estimates than was seen with 35S or 14C. Results were similar for both Ultrofilm and Hyperfilm with all the radioisotopes. These findings demonstrate a simple linear relationship between plastic and brain paste 14C-labeled standards and between either 14C-labeled standards and 35S-labeled brain paste for use in quantitative autoradiography.